package com.xxl.job.core.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.net.ServerSocket;

/**
 * net util
 *
 * @author xuxueli 2017-11-29 17:00:25
 */
public class NetUtil {

  private static Logger logger = LoggerFactory.getLogger(NetUtil.class);

  /**
   * find avaliable port
   *
   * @param defaultPort
   * @return
   */
  public static int findAvailablePort(int defaultPort) {
    int portTmp = defaultPort;
    while (portTmp < 65535) {
      if (!isPortUsed(portTmp)) {
        return portTmp;
      } else {
        portTmp++;
      }
    }
    portTmp = defaultPort--;
    while (portTmp > 0) {
      if (!isPortUsed(portTmp)) {
        return portTmp;
      } else {
        portTmp--;
      }
    }
    throw new RuntimeException("no available port.");
  }

  /**
   * check port used
   *
   * @param port
   * @return
   */
  public static boolean isPortUsed(int port) {
    boolean used = false;
    ServerSocket serverSocket = null;
    try {
      serverSocket = new ServerSocket(port);
      used = false;
    } catch (IOException e) {
      logger.info(">>>>>>>>>>> xxl-job, port[{}] is in use.", port);
      used = true;
    } finally {
      if (serverSocket != null) {
        try {
          serverSocket.close();
        } catch (IOException e) {
          logger.info("");
        }
      }
    }
    return used;
  }

}
